Treatment of hydrocarbon distillates with a phenylene diamine, a carboxylic acid salt of an amine and oxygen



ited States Patent TREATMENT or HYDROCARB'ON n'rs'rrnmrns WITH A PHENYLENE DIAMINE, A citnox- YLIC ACID SALT or AN AMINE AND OXYGEN Joseph A. Chenicek, Bensenville, Ili., assignor .to Universal Oil Products Company, Des Plaines, iii., a corporation of Delaware No Drawing. Application .May 21, .1954,

Serial 'NO.431,612

10 Claims. (Cl. 1629) 'This invention relates to the treatment ofhydrocarbon 'dist illates and more particularly to a novel method "of effecting sweetening of sour hydrocarbon 'distillates.

One method of sweetening a sour hydrocarbon distillate and particularly 'craeked gasoline entails the use'of a phenylene diamine compound. Because the phenylene diamine compound also serves as an oxidation inhibitor, this process is referred to as inhibitor sweetening.

In one embodiment the present invention is directed to an improvement in the .inhibitor sweetening process using the phenylene diamine compound. It is understood that the novel method of the present invention maybe used with other inhibitors which possess the property of also effecting sweetening of hydrocarbon 'distilla'te's.

When employed in conjunction with inhibitor s'weetem ing utilizing a phenylene diamine compound, the present process ofiers the advantage of effecting sweetening "of the sour hydrocarbon distillates ina shorter period of time. This accelerated sweetening is important to there; finer in many cases because, due to the shortage of storage capacity or in order to comply with shi ping schedules or for other reasons, it is often necessary to transport or use the distillate as soon as possible, and the refiner cannot afford to wait until sufficient time has elapsed for the distillate to become sweet. Another advantage to the process of thepresent invention is that the salt, to be hereinafter defined in detail, also serves to retard corrosion of metal surfaces contacted by'the hydrocarbon distillate. y

In one embodiment the present invention relates to a method of sweetening a sour hydrocarbon distillate which comprises contacting said distillate in the presence of an inhibitor-sweetening agent and an oxidizing agent with a carboxylic acidsalt of an amine.

In a specific embodiment the present invention relates to a process of sweetening sour cracked-gasoline which comprises contacting said gasoline in the presence of air with a phenylene diamineinhibitor and a poly'basic car;-

boxylic acid salt of an alkylene polyamine.

As hereinbefore set forth, the salt for use in accordance with the present invention in sour hydrocarbon distillates is used along with a .phenylene diamine inhibitor 2 basic carboxylic acid salt of an alkyl alkylene 'poly'aniine, the alkyl group being derived from a fatty acid.

Any-suitable amine may be utilized in preparing the additive "of the present invention. While amines including methyl amine, ethyl amine, propyl amine, butyl amine, amyl amine,-hexyl amine, etc., N-substi'tuted alkyl or other inhibitor compound possessing sweeteningproperties, referred to herein as inhibitorsweetening agent. The salt comprises a carboxylic acid salt of an amine and preferably a .polybasic carboxylic add salt of an :al-' kylene polyamine. The particular carbox'ylic acid and amine to be employed in preparing the additive may vary considerably depending upon the particular hydrocarbon distillate in which it is to be used. lngeneral the carboxylic acid and the amine will be selected so that-the resultant salt is readily soluble in the hydrocarbon distillate in the concentration of salt to -be employed. :a general rule it is preferred that the total number of carbon atoms in the salt is at least 20. As will be hereinafter set forth in detail, a preferred additive comprises a iatty ami'nes, cycloalkyl amines, cycloalkyl diamine's, cycloalkyl triamines, N-sub'stituted cycloalkyl amines, aniline, N-substitute'd -anilines, phenylene diarnine, ,phenylene friamine s, N-substituted phenylene polyarnines, etc., maybe used, it is preferred to employ alkylene polyamines. The alkylene polyamines include ethylene diamine, propylene diarnine, butylene diamine, amylene diamine, hexylene diamine, etc., as well as triamines including, for example, diet hylene triamine, dipropylene triamine, dibutylene n amine, etc., other polyamines including, for ex mple, tetraethylene pentamine, te'trapropylene pen'tan iine, te trabutylene pentamine, etc. As hereinbefore set forth, the additive contains a sufficient number of carbon atoms so that it is readily soluble in the hydrocarbon distillate. Conveniently, the carbon atoms are included as a hydrocarbon snbstituent attached to the alkylene .polyamine. While the hydrocarbon substituent maybe cyclic, including, for example, aryl, aralkyl, cycloalkyl, etc., or such groups as well as alkyl groups containing non-hydrocarbon substituents, including those containing nitrogen, sulfur, oxygen halogen, etc., it is preferred that the substitnent'is an alkyl group. The preferred alkyl alkylene polyamines maybe illustrated by the following general formula:

, R-NHR'-NHR" where R and R are selected from hydrogen and alkyl groups, at least one of which being an alkyl group, and where R'-is an alkylene radical. R or R preferably comprises an alkyl group of at least six carbon atoms'and more preferably of at least 10 carbon atoms. 7

A particularly preferred alkyl alkylene diamine eomprises one in which R is a propylene radical, R 'isan alkyl group derived from tallow and R" is hydrogen. This alkyl alkylene diamine is commercially available under the trade name of Duomeen T. Other substituted propylene diamines comprise those in which R is an alkyl group derived from lauric acid, coconut oil, 'soya oil, etc. The alkyl propylene diamines "set forth above are-available commercially 'at the presenttime' and comprise mixed alkyl substituted propylene diaminfes'. For'example, in the case of Duomeen T, the alkyl substituent contains from about '12 to about 20 carbon atoms per :group and mostly containing 16 to 18 carbon atoms. :However, when desired, the alkyl alk'ylene polyamine may be prepared to contain any number of carbon atoms desired in the R and/or R groups. Thus, one or both of these groups may be selected from rnethyl, ethyl,

propyl, butyl, amyl, hexyl, heptyl, octyl, nonyl, decy'l, u'n'decyl, dodecyl, tridecyl, pentadecyl, hexadecyl, octadecyl, nonadecyl, eicosyl, etc., it generally being preferred that one of R or R'' is hydrogen and the other is a'n alkyl group of at least six and still more preferably of at least 10 carbon atoms. It is understood that a mixture of dif fer'ent amines may be employed when desired.

any suitable carboxylic acid maybe utilizedin forming the salt of the amine and may be mono- 'or polybasic.

The specific carboxylic acid to be employed will De-selected with regard to the particular polyamine employed,

, so that the resultant salt will be readily *s'oltible' in the hydrocarbon I distillate, and "thus preferably contains comprise formic, acetic, propionic, bnt-yric, 'yaler i atlea'st six. and-still more preferably atfleast 10 carbon atoms per molecule. While the carboxyl'ic aeia' nray methyl acetic, oxalic, malonic, succinic, *glntarie; itaconic, mesaconic, eitraco'nic, glutaconic, etc., it preferably eon "ensure tains at least six carbon atoms, referred to herein as high molecular weight carboxylic acid, and, therefore, is selected from caproic, heptylic, caprylic, adipic, pimelic, suboric, azelaic, sebacic, phthalic, etc., capric, lauric, myristic, palmitic, stearic, arachidic, behinic, lignoceric, cerotic, decylenic, dodecylenic, palmitoleic, oleic, ricinoleic, petroselinic, vaccenic, linoleic, linolenic, eleostearic, licanic, parinaric, tariric, gadoleic, arachiodonic, cetoleic, erucic, selacholeic, etc., aconitic, citric, gluconic, etc., hemimellitic, trimellitic, trimesic, prehnitic, mellophanic, pyromellitic, mellitic, and higher molecular weight carboxylic acids. It is understood that a mixture of acids may be employed. A particularly preferred acid comprises a mixed by-product acid being marketed commercially under the trade name of VR-l Acid. This acid is a mixture of polybasic acids and may contain from about 30 to about 50 carbon atoms per molecule.

Another particularly preferred acid comprises tall oil acid which isa mixture of rosin acids and fatty acids and contains an average of about 16 carbon atoms per molecule.

The salt may be acid, neutral or basic. The acid salt generally is preferred. The neutral salt is prepared by utilizing stoichiometric amounts of the acid and amine. In other words, the concentration of carboxylic acid and amine will be selected so that there will be an equivalent number of carboxylic acid groups to amino groups. Thus, the specific concentrations will depend upon whether the acid is monobasic, dibasic, tribasic or higher polybasic acid, and whether the amine is monoamine, diamine, triamine or higher polyamine. The acid salt is prepared by utilizing a deficiency of amino groups in relation to the carboxylic acid groups as, for example, by utilizing one equivalent of amine to two equivalents of carboxylic acid. The basic salt is prepared' by utilizing a deficiency of carboxylic acid groups in relation to the amine groups as, for example, by utilizing one equivalent of carboxylic acid per two equivalents of amine. It is understood that these different salts are not necessarily equivalent.

The salt may be prepared in any suitable manner and, in general, is readily prepared by admixing the acid and amine at ambient temperature, preferably with vigorous stirring. Y The salt is readily prepared at room temperature, although slightly elevated temperature which generally will not exceed about 200 F. may be employed when desired. Excessive temperature should not be utilized because of the undesired formation of amides or other reaction products. Depending upon the particular amine and acid employed, it may be desirable to utilize a solvent either in forming a more fluid mixture of the acid and/or amine before mixing or during the mixing thereof. In some cases it may be desirable to admix the salt with the solvent in order to form a more fluid final product and the solvent conveniently may comprise an organic compound and particularly a hydrocarbon distillate.

The amount of salt to be employed will depend upon the particular salt and the particular hydrocarbon dis- .tillate in which it is to be used. In general, the salt will be used in a concentration of less than about 1% by weight and preferably within the range of from about 0.0001% to about 1% by weight of the hydrocarbon distillate. However, in some cases the salt may be used in larger concentrations which generally will not exceed about 5% of the hydrocarbon distillate. The larger concentrations may be desired when use in a system of excessive corrosion in order to reduce the corrosion as, well as to obtain sweetening of the hydrocarbon distillate. The corrosion occurs in the presence of water and the salt appears to form a protective film around the metal surfaces and thereby serves to avoid corrosion by the water contained in the system.

As hereinbefore set forth the inhibitor used in conjunction with the salt is preferably a phenylene diamine inhibitor. Any suitable phenylene diamine inhibitor may amyl-p-phenylene be used in accordance with the present invention. The preferred phenylene diamine inhibitor comprises N,N'-disecondary-butyl-p-phenylene diamine. Other phenylene diamine compounds include N,N-di-propyl-p-phenylene diamine, N,N-di-butyl-p-phenylene diamine, N,N'-didiamine, N,N'-di-hexyl-p-phenylene diamine, N,N-di-heptyl-p-phenylene diamine, N,N'-dioctyl-p-phenylene diamine, N,N'-di-nonyl-p-phenylene diamine, N,N'-di-decyl-pphenylene diamine, N,N-diundecyl-p-phenylene diamine, N,N'-di-dodecyl-p-phenylene diamine, N,N-di-tridecyl-p-phenylene diamine, N,- N'-di-tetradecyl-p-phenylene diamine, N,N-di-pentadecyl-p-phenylene diamine, N,N-di-hexadecyl-pphenylene diamine, N,N'-di-heptadecyl-p-phenylene diamine, N,N'- di-octadecyl-p-phenylene diamine, N,N'-di-nonadecyl-pphenylene diamine, N,N'-di-eicosyl-p-phenylene diamine, etc. In general, it is preferred that the aliphatic groups are branched groups as in compounds including N,N'-diisopropyl-p-phenylene diamine, N,N-disecondary-amylp-phenylene diamine, N,N'-di-secondary-hexyl-p-phenylene diamine, N,N'-di-secondary-heptyl-p-phenylene diamine, N,N'-di-secondary-octyl-p-phenylene diamine, etc. Usually, both aliphatic groups will be the same but in some cases they may be diiferent as in such compounds as N-isopropyl-N-secondary-butyl-p-phenylene diamine, N-isobutyl-N'-secondary-amyl-p-phenylene diamine, N- isopropyl-N'-secondary-hexyl-p-phenylene diamine, N-

isopropyl-NFsecondary-heptyl-p-phenylene diamine, etc.,

N-secondary-butyl-N-secondary-amyl-p-phenylene diamine, N-secondary-butyl-N-secondary-hexyl-p-phenylene diamine, N-secondary-butyl-N-secondary-heptyl-p-phenylene diamine, N-secondary-butyl-N-secondary-octyl-pphenylene diamine, etc. It is understood that these various' phenylene diamine compounds are not necessarily equivalent. The phenylene diamine compound usually will be employed in a concentration of from about 0.000l% to about 1% and more particularly in a concentration of from about 0.0005% to about 0.05% by weight of the hydrocarbon distillate.

' While the use of the salt with a phenylene diamine inhibitor comprises a preferred embodiment of the present invention, it is understood that the salt may be used along With other inhibitor compounds which also possess sweetening properties. In general, these inhibitors are amine type and more particularly aromatic diamine compounds.

'An illustrative inhibitor of this type comprises an orthoamino-diphenyl amine and particularly an ortho-alkylamino diphenyl amine including such compounds as ortho-amino diphenyl amine, ortho-isopropyl amino diphenyl amine, ortho-sec-butylamino diphenyl amine, o'rtho-sec-amylamino diphenyl amine, ortho-sec-hexylamino diphenyl amine, ortho-sec-heptylamino diphenyl amine, ortho-sec-octylamino diphenyl amine, ortho-secnonylamino diphenyl amine, ortho-sec-decylamino diphenyl amine, ortho-sec-undecylamino diphenyl amine,

'ortho-sec-dodecylamino diphenyl amine, etc. It is understood that one or both of the aromatic rings may contain 'substituents and particularly alkyl groups attached thereto' and also that the ortho nitrogen atom may contain two hydrocarbon groups and particularly alkyl groups attached thereto. It is understood that these inhibitor compounds are not necessarily equivalent.

As hereinbefore set forth, the concentration of the salt-and phenylene diamineinhibitor each may be within the range of from about 0.0001% to about 1% by weight.

It generally is preferred that the concentration of salt and the concentration of phenylene diamine inhibitor be within the ratio of at least 10 weight percent of one component to weight percent of the other component and still more preferably at least 30 weight percent of one component to 100 weight percent of the other component. a

The use of the salt in combination with the phenylene diamine or other inhibitor offers numerous advantages over the use of the phenylene diamine or other inhibitor gas-75417.2

alone. As hereinb'e'fore "set forth, this :re'suIts in faster sweetening and therefore permits the refiner to'transp'ort or use the hydrocarbon distillate at an earlier date. Furthermore, the amount of phenylene diamine inhibitor to be employed may be less than that required in the "absence of the salt. Still further, the use of these two types of compounds appears to exert a synergistic eifect in the inhibitor sweetening reaction, and this may serve to effect sweetening of some hydrocarbon distillates which do not respond to the use of either compound alone. Another advantage to the use of the salt of the present invention is that it serves to retard and/or prevent corrosion in contact with water which normally is encountered during processing, transportation and/or use of the hydrocarbon distillate.

While the use of the .salt in conjunction with the phenylene diamine or other inhibitor is preferred, in some cases, one of the reactants forming the salt (that is, the amine or carboxylic acid) may be used in conjunction with the phenylene diamine or other inhibitor. With certain hydrocarbon distillates, the use of the amine and particularly an alkyl alkylene polyamine or the use or the carboxylic acid and particularly a higher molecular weight polycarboxylie acid will serve to accelerate inhibitor sweetening. The extent of acceleration of the inhibitor sweetening may be sufiicient in a particular instant. However, as hereinbefore set forth, it usually is preferred to use the salt inorder to obtain the optimum eifect.

Because the sweetening reaction includes the conversion of mercaptans to disulfides, presumably through an oxidation reaction, it is essential that air or other oxidizing agent be present in the reaction. Generally sufficient air will be dissolved or entrained in the hydrocarbon distillatein order to satisfy this requirement. However, when sufficient air is not so dissolved, air from an extraneous source may be added to the hydrocarbon distillate. It is understood that oxygen or other oxygen-containing gases may be used in place of air. -In some casesot her oxidizing agents such as peroxides, permanganates, etc. may be employed.

In general, it is preferred to e'ifec't the sweetening in'the presence of an alkaline reagent. Generally the alkaline reagent will be used in small amounts which usually 'will not exceed about 5% by weight of the hydrocarbon distillate. For convenience in the subsequent separation, the alkaline reagent preferably comprises an aqueous solution thereof. Usually the hydrocarbon distillate is subjected to pretreatment with an alkaline reagent in order to remove a major proportion of the 'mercapt'ans contained in the distillate. Conveniently the aqueous solution of alkaline reagent used in the sweetening comprises the same solution used to pretreat the hydrocarbon distillate. In some cases, a sufficient amount of alkaline solution is entrained in the hydrocarbon distillate after such pretreatment and may be sufficient foreffe'cting the sweetening. Preferred alkaline solutions comprise aqueous solutions of caustic (sodium hydroxide), potassium hydroxide, etc. I

The process of the present invention may be effected in any suitable manner whereby the hydrocarbon distillate is intimately contacted with the additive. In a preferred method, the salt and phenylene diamine or other inhibitor are commingled with the hydrocarbon stream and the resultant mixture is passed through suitable mixing devices such as durion mixers, orifice mixers, etc. mixture is then passed into a storage tank, which, when desired, may contain suitable stirring means such as mixing paddles, etc. to effect further mixing of the components therein. If sutficient air is not contained in the hydrocarbon distillate, air or other oxygen containing gas .may be introduced directly into'the storage tank or it may be supplied to the stream of hydrocarbon distillate before or after mixing with the salt. Similarly, if sufficient alkaline reagent is not present in the hydrocarbon dis- The resultant tillate, it inay be "commingled with the hydrocarbon stream beforeor after mixing of'the'other components or it "may be 'supplieddir'ectly to the storage tank. In still another embodiment the salt may be introduced into a fractionator or other plant equipment in which the-hydrocarbon distillate is being treated in order to retard corrosion of the plant equipment. In this embodiment, an excess of the saltis utilized so that part of the salt will be employed in retarding corrosion and another part ofthe salt will remain dissolved in the hydrocarbon distillate for subsequent sweetening, preferably upon the later cornmingling of the phenylene diamine inhibitor with the hydrocarbon distillate. H

The sweetening of the present invention is readily effected at atmospheric temperature which generally ranges from about 50 to about F. However, in some cases it may be desirable to utilize elevated temperatures which may range up to F. or more.

While this process is particularly applicable for the treatment of cracked gasoline, it is understood that, with suitable modification, the process may be utilized for the treatment ofstraight run and/ or natural gasoline or mixtures thereof with cracked gasoline, as well as cracked and/ or straight run higher boiling hydrocarbon distillates including jet fuel, kerosene, diesel fuel, burner oil, lubricating oil,.gas oil, etc.

The following examples are introduced to illustrate further the novelty and utility of the present invention but not with the intention of unduly limiting the same.

EXAMPLE I The gasoline used in this example was a Pennsylvania thermally cracked gasoline which had been treated with caustic-methanol to remove mercaptans and then asufiicient amount of n-hexyl mercaptan was added to produce a final gasoline containing about 0.0240% by weight of mercaptan sulfur. The gasoline as prepared in this man- 'ner offers the advantage of providing a gasoline of uniform mercaptan content and is a more reliable standard for comparing the results obtained with the various additives.

The :results reported in this example were obtained by utilizing 400 ml. samples of the gasoline, which are poured into separate pint bottles along with 40 ml. of a 1% aqueous sodium hydroxide solution. The bottles were capped with corks containing 1 mm. capillary vents and stored in the dark at 100 F. The change in me'rcaptan concentration was followed by periodic electrometric titration with 0.01 N alcoholic silver nitrate solution.

A sample of the gasoline was'used as a control or blank sample and this sample contained no additives. To another sample of the gasoline, 0.005% by weight of N,N'- di-sec-butyl-p-phenylene diamine was added. To still anothersample'of the gasoline, 0.005% by weight of N,N- di-sec-butyl-p-phenylene diamine and 0.0025% by weight of the acid salt prepared from Duomeen T and VR-l Acid was added. The .salt was used as approximately a 50% solution in a hydrocarbon distillate. The concentration used is on the basis of the solution and, therefore, the percent of active constituent is approximately /2 of that specified above. The results of these runs are shown in the following table.

- Table I Percent Mercaptan Sulfur Content after about 2 days storage Additive It will be noted from the above data that, with this particular gasoline, the use of N,N-di=secabutyl pphenyl- 7 ene diamine alone resulted in a mercaptan sulfur content of about 0.01% by weight after 2 days storage, whereas the use of both this additive and the salt described above lowered the mercaptan sulfur content after 2 days storage to 0.0004%.

EXAMPLE 11 After about 3 days storage of the samples described in Example I, the sample containing N,N-di-sec-butyl-pphenylene diamine had a mercaptan sulfur content of 0.0058%, whereas the sample containing both this additive and the salt was sweet. Thus, it is seen that a sweet gasoline was obtained in about 3 days by using both of these additives and, as hereinbefore set forth, this permits the refiner to transport and/or use the gasoline at an earlier date.

The sample of gasoline containing no additive still had a mercaptan sulfur content of 0.0174% after about 7 days in storage.

EXAMPLE III As mentioned in Example I, the salt used was approximately a 50 percent solution. In this example, the salt was not prepared as a solution but comprised 100% active constituent. When utilized in a concentration of 0.0025% by weight along with 0.005% by weight of N,N'-di-secbutyl-p-phenylene diamine, another sample of the gasoline was sweet after about 2 days storage.

EXAMPLE IV This example illustrates the results when using a commercial catalytically cracked gasoline. After about 3 days storage at 100 F., the mercaptan sulfur content of a sample of the gasoline was 0.0192% by weight. The addition of 0.005% by weight of N,N-di-sec-butyl-pphenylene diamine to another sample of the gasoline reduced the mercaptan sulfur content after about 3 days to 0.0045 However, the addition of both 0.005% by weight of N,N'-di-sec-butyl-p-phenylene diamine and 0.00025% by weight of the acid salt described in Example III (no solvent) reduced the mercaptan sulfur content of the gasoline to 0.0005% by weight after about 3 days storage. Here again, it will be noted that the use of both additives resulted in considerably accelerated sweetening.

EXAMPLE V In this example, 0.004% by weight of N,N'di-sec-butylp-phenylene diamine and 0.0002% by weight of the acid salt were utilized. In another sample of the gasoline described in Example IV, after about 3 days storage the mercaptan sulfur content of the gasoline was 0.0025

EXAMPLE VI The salt used in this example was the neutral salt prepared from Duomeen T and VR-l Acid in the manner hereinbefore set forth. 0.005% by weight of the neutral salt along with 0.005% by weight of N,N-di-secbutyl-p-phenylene diamine were utilized and this served to reduce the mercaptan sulfur content of the gasoline from 0.0240% to 0.0031% after about 2 days storage.

EXAMPLE V II The inhibitor compound of this example comprises ortho-isopropyl amino diphenyl amine. When used in a concentration of 0.003% by weight along with 0.003% by weight of the acid salt prepared from Duomeen T and VR-l Acid," sweetening of thegasoline will be accelerated.

EXAMPLE VIII To another sample of 'the gasoline described in Example I, tert-hexyl mercaptan was added and different samples thereof were stored in the same manner as hereinbefore set forth. After about 4 days in storage, the sample containing no additive had a mercaptan sulfur content of about 0.0207% by weight. The sample to which 0.005% by weight of N,N-di-sec-butyl-p-phenylene diamine was added had about the same mercaptan sulfur content after about 4 days in storage. However, the sample to which 0.005% by weight of N,N'-di-sec-butylp-phenylene diamine and 0.0025 by weight of the acid salt were added had a mercaptan sulfur content of 0.0094% by weight after about 4 days storage. It will be noted that with this particular mercaptan, the N,N di-sec-butyl-p-phenylene diamine was not effective but that the use of both this addtiive and the salt resulted in a considerable reduction in the mercaptan sulfur content of the gasoline.

EXAMPLE IX A salt for use in accordance with the present invention may be prepared as follows: The polyamine comprises lauryl-1,4-butylene diamine, the lauryl radical being the alkyl group derived from lauric acid. The carboxylic acid used in this example is oleic acid. In order to obtain corrosion protection, the acid salt is prepared by employing two equivalents of the acid per one equivalent of the amine.

This salt is mixed with an equal proportion of orthoisopropyl amino diphenyl amine, and the resultant mixture is utilized in a concentration of about 0.005% by weight to effect sweetening of sour cracked kerosene.

I claim as my invention:

1. The method of sweetening a sour hydrocarbon distillate which comprises contacting said distillate in the presence of an oxidizing agent with an inhibitor-sweetening agent and a carboxylic acid salt of an amine.

2. The method of sweetening a sour hydrocarbon distillate which comprises contacting said distillate in the presence of an oxidizing agent with an inhibitor-sweetening agent and a polybasic carboxylic acid salt of an alkylene polyamine.

3. A method of sweetening a sour hydrocarbon distillate which comprises contacting said distillate in the presence of air with an inhibitor-sweetening agent and a polybasic carboxylic acid salt of an alkyl alkylene polyamine.

4. The method of sweetening a sour hydrocarbon distillate which comprises contacting said distillate in the presence of an oxidizing agent and an alkaline reagent with an inhibitor-sweetening agent and a polybasic carboxylic acid salt of an alkyl propylene diamine.

5. The method of sweetening a sour hydrocarbon distillate which comprises contacting said distillate in the presence of an oxidizing agent with a phenylene diamine inhibitor and a carboxylic acid salt of an amine.

6. The method of sweetening a sour hydrocarbon distillate which comprises contacting said distillate in the presence of air with a phenylene diamine inhibitor and a carboxylic acid salt of an alkylene polyamine.

7. The method of sweetening sour gasoline which comprises contacting said gasoline in the presence of air with a phenylene diamine inhibitor and a polybasic carboxylic acid salt of an alkylene polyamine, and retaining the resultant mixture in storage at a temperature of from about 50 to about F. until the gasoline is substantially sweet.

8. The method of sweetening sour cracked gasoline which comprises contacting said gasoline in the presence of air and sodium hydroxide with N,N-di-sec-butyl-pphenylene diamine and an acid salt of a polybasic carboxylic acid containing from about 30 to 50 carbon atoms per molecule and an alkyl propylene diamine said alkyl containing from about 12 to about 20 carbon atoms.

9. The method of claim 8 further characterized in that said N,N-di-sec-butyl-p-phenylene diamine and acid salt are each used in a concentration of from about 0.00019?) to about 1% by weight of the gasoline.

10. The process of claim 9 further characterized in that the concentration of acid salt is at least 30 weight percent of said N,N'-di-sec-butyl-p-phenylene diamine.

References Cited in the file of this patent UNITED STATES PATENTS 

1. THE METHOD OF SWEETENING A SOUR HYDROCARBON DISTILLATE WHICH COMPRISES CONTACTING SAID DISTILLATE IN THE PRESENCE OF AN OXIDIZING AGENT WITH AN INHIBITOR-SWEETENING AGENT AND A CARBOXYLIC ACID SALT OF AN AMINE. 